A synthetic zeolite is crystalline aluminosilicate, and has uniform pores that are attributed to a crystal structure thereof and has an angstrom size. Taking advantage of such a feature, the synthetic zeolite is industrially used as a molecular sieving adsorbent that adsorbs only a molecule having a specific size, an adsorption separating agent that adsorbs a molecule having strong affinity, or a catalytic base. A beta zeolite that is one of such zeolites is currently used in quantity as a catalyst in the petrochemical industry or an adsorbent for vehicle exhaust gas treatment throughout the world.
A method of synthesizing the beta zeolite is variously proposed. A typical method is a method of using a surfactant of a tetraethylammonium ion and the like, as an organic structure defining agent (hereinafter abbreviated to “OSDA”). However, a compound containing the tetraethylammonium ion is expensive, and what is more, most of the compound is decomposed after beta zeolite crystallization is terminated. As such, it is impossible to recover and reuse the compound. For this reason, the beta zeolite produced by such a method is expensive. Further, since the tetraethylammonium ion is incorporated into a crystal of the beta zeolite, it is necessary to fire the beta zeolite to remove the tetraethylammonium ion when the beta zeolite is used as the adsorbent or the catalyst. In that case, exhaust gases are responsible for environmental pollution, and further, many chemicals are required for detoxification treatment of a synthetic mother liquid. In this way, the method of synthesizing the beta zeolite using the tetraethylammonium ion is not only an expensive method but also a production method having a great environmental load. As such, there is a need to realize a production method of using no OSDA.
Therefore, the applicant has proposed a production method of producing a beta zeolite using no OSDA (see Patent Document 1). According to this method, there is an advantage that self-reproduction of the beta zeolite is infinitely possible without using the OSDA.
Incidentally, as a porous crystal having a pore of a mesopore region, a mesoporous molecular sieve including MCM-41 is known. Since the OSDA is still used for synthesis of the mesoporous molecular sieve, the aforementioned disadvantage is present.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2011-126768